The present invention relates to an oil cylinder for a stand carriage. More particularly, the present invention relates to an oil cylinder for a stand carriage in a hospital.
Referring to FIGS. 1 to 3, a stand carriage comprises a U-shaped frame 1, four casters 6 connected to the U-shaped frame 1, a support frame 2 disposed on the 10 U-shaped frame 1, a bracket rod 3 disposed on the support frame 2, a support rod 54' disposed on the support frame 2 pivotally, an oil cylinder 5' disposed on the support rod 54', a shaft 53' extending from the oil cylinder 5' and connected to the bracket rod 3, and a button 52' disposed on the oil cylinder 5' to control the oil in the oil cylinder 5'. A hook device 4 is hung on the bracket rod 3. The oil cylinder 5' comprises a valve body 59', an oil pressure chamber 56', and an oil storage chamber 55'. A piston chamber 591' is disposed in the valve body 59'. A piston 57' is disposed in the piston chamber 591'. An annular groove 571' is formed on the piston 57'. An arc-shaped through hole 592' is formed in the valve body 59' communicating with the piston chamber 591'. A trip lever 512' passes through the arc-shaped through hole 592' and inserted in the annular groove 571'. An enlarged hole 597' is formed in the valve body 59' receiving a rotating post 511'. The trip lever 512' is connected to the rotating post 511' eccentrically. The rotating post 511' can be rotated in the enlarged hole 597' freely. A first oil passage 593' is formed in the valve body 59' communicating with the oil storage chamber 55'. A second oil passage 594' is formed in the valve body 59' communicating with the first oil passage 593'. A third oil passage 596' is formed in the valve body 59' communicating with the second oil passage 594'. A fourth oil passage 595' is formed in the valve body 59' communicating with the oil pressure chamber 56'. A big ball 501' is placed between the third oil passage 596' and the second oil passage 594'. A small ball 502' is placed between the second oil passage 594' and the first oil passage 593'. A bolt 581' is inserted in the third oil passage 596'. A compression spring 582' is connected to the bolt 581' and the big ball 501'. A coiled spring 583' is connected to the big ball 501' and the small ball 502'. The big ball 501 ' seals a first end of the second oil passage 594'. The small ball 502' seals a second end of the second oil passage 594'. The second oil passage 594' communicates with the piston chamber 591'. A swivel rod 51' is connected to the rotating post 511'. When the swivel rod 51' is operated, the rotating post 511' drives the trip lever 512' to move reciprocally. Therefore, the piston 57' can move upward and downward alternately. When the piston 57' moves downward, the oil in the oil storage chamber 55' flows into the first oil passage 593'. The small ball 502' is forced to move leftward so that the oil can flow into the piston chamber 591'. When the piston 57' moves upward, the oil in the piston chamber 591' flows into the third oil passage 596', the fourth oil passage 595', and the oil pressure chamber 56'. Since the shaft 53' extends from the oil pressure chamber 56', the shaft 53' will move upward to lift the bracket rod 3. An O-ring oil seal (not shown in the figures) is disposed in the piston chamber 591'. An oil hole 598' in the valve body 59' communicates with the third oil passage 596'. A steel ball (not shown in the figures) seals an end of the oil hole 598'. However, the O-ring oil seal cannot prevent the leakage of oil effectively. A V-ring oil seal can prevent the leakage oil effectively. Since the piston chamber 591' is very narrow, a V-ring oil seal cannot be disposed in the piston chamber 591'. Furthermore, the piston chamber 591' is too narrow and too deep to be fabricate precisely. Therefore, the motion of the piston 57' will be influenced. The operation of the oil cylinder 5' will be influenced also.